Lubricant composition



United States Patent 3,546,116 LUBRICANT COMPOSITION Quentin E.Thompson, Belleville, Ill., assignor to Monsanto Company, St. Louis,Mo., a corporation of Delaware No Drawing. Filed Mar. 3, 1967, Ser. No.620,280 Int. Cl. Cm 1/20 US. Cl. 25242.7 9 Claims ABSTRACT OF THEDISCLOSURE Compositions of the class which exhibit improved oxidationresistance by the incorporation of certain alkali metal compounds into aclass of base stocks, representative of which are monoesters, diesters,triesters, polyesters, complex esters and mixtures thereof. Thecomposition have many uses, among which are jet engine lubricants andhydraulic fluids.

This invention relates to functional fluid compositions which exhibitimproved oxidative stability together with improved resistance to thecorrosion of metal surfaces and more particularly to functional fluidcompositions comprising certain functional fluids and an additive amountof an alkali metal compound.

Many different types of materials have been utilized as functionalfluids and functional fluids are used in many different types ofapplications. Such fluids have been used as electronic coolants, atomicreactor coolants, diffusion pump fluids, synthetic lubricants, dampingfluids, bases for greases, force transmission fluids (hydraulic fluids),heat transfer fluids, die casting release agents in metal extrusionprocesses and as filter mediums for air conditioning systems. Because ofthe wide variety of ap plications and the varied conditions under whichfunc tional fluids are utilized, the properties desired in a goodfunctional fluid necessarily vary with the particular application inwhich it is to be utilized with each individual application requiring afunctional fluid having a specific class of properties.

Of the foregoing the use of functional fluids as lubricants,particularly jet engine lubricants, has posed what is probably the mostdifficult area of application. As the operating temperatures forlubricants have increased it has become exceedingly diflicult to findlubricants which properly function at engine temperatures for anysatisfactory length of time. Thus, the requirements of a jet enginelubricant are as follows: The fluid should possess high and lowtemperature stability, foam resistance, good storage stability and benoncorrosive and nondamaging to metal mechanical members which are incontact with the fluid. Such fluids should, in addition, possessadequate temperature-viscosity properties and satisfactory lubricity,that is, the lubricants must not become too thin at the very hightemperatures to which they are subjected nor must they become too thickat lower temperatures and must at the same time be able to providelubricity over such range of temperatures. In addition, such lubricantsshould not form deposits which interfere with the proper operation of ajet engine.

As the speed and altitude of operation of jet engine containing vehiclesincreases, lubrication problems also increase because of increasedoperating temperatures and higher bearing pressures resulting from theincreased thrust needed to obtain high speeds and altitudes. As theService conditions encountered become increasingly severe the usefullife of the functional fluid is shortened, primarily due to theirdeficiency in oxidative stability above 450 F. In general, as theoperating requirements "ice of a jet engine are increased, enginetemperatures increase and oil tempeartures in the range of 500 F. andhigher are encountered.

The useful life of any lubricant can be adjudged on the basis of manycriteria such as the extent of viscosity increase, the extent ofdeposits and the extent of corrosion to metal surfaces in contact withthe lubricant. Those skilled in the art have found many ways to improvelubricants and to thus retard or prevent the effects which shorten theuseful life of a lubricant. Thus, it is a general practice to add smallamounts of other materials,, or additives, to lubricants in order toaffect one or more of the properties of the base lubricant. It isdifficult, however, especially as operating temperatures are increased,to find additives which will still perform the function for which theyare added and yet not inject other problems such as increasing corrosionand engine deposits.

One of the major problems that occurs when a fluid oxidizes is theformation of oxidation products which can form sludge and deposits andin addition chemically attack both the fluid and mechanical members incontact with the fluid. In addition to the inhibition and control ofoxidation of a fluid, such as by the incorporation of an antioxidant,the antioxidant itself must perform its function without injecting otherproblems, such as increasing corrosion of metal surfaces. As is readilyapparent from the aforedescribed uses of a functional fluid, a fluid,depending upon the application, contacts various metals as for example,lead, aluminum, copper, bronze, steel and many alloys, which alloysutilize many types of metals in the allow composition. Corrosion ofmechanical members such as bearing cages having lead flashings adverselyaffects (1) the mechanical members of a system in contact with thefluid, (2) the functional fluid itself and (3) the lubrication functionof the fluid. The main problem resulting from corrosion of mechanicalmembers, especially lead corrosion, is the effect of the corrosionproducts on the functional fluid and the lubrication function of thefluid. The corrosion products can form deposits on the mechanicalmembers in contact with the fluid as well as being solubilized in thefunctional fluid. Certain corrosion products in addition to formingdeposits can promote oxidation by catalyzing the oxidation of afunctional fluid, thereby promoting increased sludge and depositformation.

Thus, deposits can in general be formed from the oxidation of the basestock as well as deposits formed by the corrosion of mechanical membersin contact with the fluid. The corrosion products can be formed, forexample, by the corrosion of mechanical members by the oxidized fluid orby additives which are incorporated into a given fluid. The formation ofdeposits contaminates the fluid and requires premature draining of thefluid from the system as well as filter clogging and excessive filterreplacement. In addition, deposits can adversely affect the properlubrication of bearings such as by restricting and in some casescompletely restricting the ability of a fluid to reach criticalmechanical parts so as to perform their lubrication function. Inaddition, deposits can act as insulating materials when such depositsand other insoluble materials form on mechanical members. When thisinsulating effect occurs, the fluid does not accept heat as readily frommechanical parts at temperatures higher than the fluid and as aconsequence metal fatigue and pitting of mechanical members can occur.

As is seen from the foregoing characteristics of a jet engine, afunctional fluid can attain temperatures of up to 500 F. and higherwhich can result in oxidative and thermal degradation of a lubricant.The stabilization of lubricants at these high operating temperaturesthrough the use of additives presents an extremely complex and difficultproblem, especially since the incorporation of an antioxidant can injectother problems such as increased corrosion and engine deposits. Thus,the fact that one problem is solved such as oxidative stability of afunctional fluid does not justify the introduction of an additionalproblem such as lead corrosion. As has been discussed above, depositsformed from corrosion of mechanical members can be generated by theoxidation of the base stock as well as additives incorporated into abase stock. It is, therefore, of particular importance that anantioxidant inhibit and control oxidation of a base stock as Well as notpresenting any adverse problems.

It is, therefore, an object of this invention to provide functionalfluid compositions which have improved oxidative stability by theincorporation of an antioxidant whereby said functional fluid exhibitsimproved oxidative stability together with improved resistance of thefunctional fluid composition towards the corrosion of lead surfaces incontact with functional fluids.

It has now been found that the oxidative stability and thus the usefullife of functional fluids can be greatly extended, without injectingother problems, even under the severe conditions encountered in jetengines and other devices by the addition to functional fluids of analkali metal compound selected from the group consisting of (A) (l) Acompound represented by the structure where X is selected from the groupconsisting of carbonyl and sulfonyl; R is selected from the groupconsisting of R2 0 -c'1i'J0M I". and

-c=coo R2 Ra provided that when X is sulfonyl R is R is selected fromthe group consisting of a hydrocarbon radical and a heterocyclic ringhaving from 3 to 10 atoms optionally interrupted 'by from 1 to 4 heteroatoms selected from the group consisting of oxygen, nitrogen and sulfur;Y is selected from the group consisting of oxygen, sulfur and a is awhole number having a value of from 0 to 1, provided that when R is ahas a value of 0; R and R are each selected from the group consisting ofhydrogen and a hydrocarbon radical and when R is (|1=CI3OM R2 Ra R and Rtogether with the carbon atoms to which they are attached can form anonbenzenoid carbocyclic ring having from 4 to 8 carbon atoms; R; isselected from the group consisting of hydrogen and a member of the grouprepresented by R and when a has a value of l and Y is R, and R togetherwith the nitrogen atom to which they are attached can form aheterocyclic ring having from 3 to 10 atoms optionally interrupted byfrom 1 to 4 hetero atoms selected from the group consisting of oxygen,nitrogen and sulfur and M is an alkali metal; and

(2) mixtures thereof.

(B) (l) A compound represented by the structure RfiAI-R5 wherein Ar isan aromatic nucleus selected from the group consisting of benzene,benzoquinone and naphthalene; R

is selected from the group consisting of hydroxyl, 0M and II OORs,wherein M is an alkali metal; R is Rg(Yl)c (o)d and when R occupies aposition ortho to R or when Ar is napthalene and R and R occupypositions l,8-, R and R together with the aromatic nucleus to which theyare attached can form a cyclic carbonate; 0 and d are each whole numbershaving a value of 0 to 1, provided that the sum of c1+d is from O to 1;R and R are each selected from the group consisting of a hydrocarbonradical and a heterocyclic ring having from 3 to 10 atoms optionallyinterrupted by from 1 to 4 hetero atoms selected from the groupconsisting of oxygen, nitrogen and sulfur; Y is selected from the groupconsisting of oxygen, sulfur and l io .N

R is selected from the group consisting of hydrogen and a member of thegroup represented by R and R and R together with the nitrogen atom towhich they are attached can form a heterocyclic ring having from 3 to 10atoms optionally interrupted by from 1 to 4 hetero atoms selected fromthe group consisting of oxygen, nitrogen and sulfur; d is a whole numberhaving a value of from 0 to 6; R is selected from the group consistingof a hydrocarbon oxy radical, a member of the group represented by R amember of the group represented by R and a member of the grouprepresented by R and when 11 has a value greater than 1 any two groupsrepresented by R which are attached to adjacent carbon atoms cantogether with the carbon atoms to which they are attached form a cyclicring selected from the group consisting of a carbocyclic ring and aheterocyclic ring, said cyclic ring having from 3 to 10 atoms optionallyinterrupted by from 0 to 4 hetero atoms selected from the groupconsisting of oxygen, nitrogen and sulfur; provided that when Ar isselected from benzene or naphthalene and R and R are attached to thesame carbocyclic ring, R is positioned ortho to R when d has a value of0 and R is positioned ortho or meta to R when d has a value of 1, andprovided that when Ar is naphthalene wherein R and R are attached todifferent carbocyclic rings R and R occupy positions selected from 1,5-and 1,8- and further provided that there is present at least one 0Mgroup wherein M is an alkali metal; and (2) mixtures thereof.

(C) (1) A compound represented by the structure wherein M is an alkalimetal, R and R are each selected from the group consisting of hydrogenand a hydrocarbon radical; and (2) mixtures thereof; and

(D) Mixtures of (A), (B) and (C).

The functional fluids to which the alkali metal compounds represented by(A), (B), (C) and (D) are added to provide compositions of thisinvention, hereinafter referred to as *base stocks, include by way ofexample, an ester base stock, ester base stock defined herein to includea single ester base stock as well as a mixture of ester base stocks,typical examples of which are monoester base stocks, diester basestocks, triester base stocks, polyester base stock, complex ester basestocks and mixtures thereof. It is contemplated that mixtures of theaforedescribed base stocks can contain major amounts of one base stockeven as high as 99% with the remainder being one or more base stocks.

Whereas the incorporation of any foreign element into a base stock canalter properties of a functional fluid, the concentration of the alkalimetal compounds represented by (A), (B), (C) and (D) in the base stockis adjusted in terms of the particular system and the base stock whichis utilized in this system to provide functional fluid compositions ofthis invention which contain additive amounts of an alkali metalcompound represented by (A), (B), (C) and (D) sufiicient to improve theoxidative stability of a base stock while not adversely affectingcritical functional fluid properties. It has generally been found thatthe preferred additive concentration of an alkali metal compoundrepresented by (A), (B), (C) and (.D) for the base stocks describedabove is generally from about 0.001 weight percent to about 10 weightpercent, preferably from about 0.01 weight percent to about 2.5 weightpercent.

Therefore, included within the present invention are compositionscomprising a base stock and an oxidation improving amount of an alkalimetal compound represented by (A), (B), (C) and (D), that is, an alkalimetal compound represented by (A), (B), (C) and (D) is added to thecompositions at a concentration sufficient to improve the oxidativestability. The functional fluid compositions of this invention can becompounded in any manner known to those skilled in the art, as forexample, by adding an alkali metal compound represented by (A), (B), (C)and (D) to the base stock with stirring until a composition is obtained.In addition, the metal compounds can be prepared in situ, that is, inthe base stocks as aforedescribed. It is also contemplated within thescope of this invention that additive concentrates can be prepared suchas additive compositions containing from about 10% to about 60% of thealkali metal compounds represented by (A), (B), (C) and (D) and the basestocks as aforedescribed.

Typical alkali metals are lithium, sodium, potassium, rubidium andcesium. Although all alkali metals are contemplated within the scope ofthis invention, the preferred alkali metal is potassium.

The various groups represented by a hydrocarbon radical, a hydrocarbonoxy radical, a cyclic ring, a carbocyclic ring and a heterocyclic ringare defined broadly to include groups which are unsubstituted as well assubstituted. In the following discussion the term hydrocarbon radicalincludes not only a group represented by a hydrocarbon radical but inaddition includes the hydrocarbon portion of the hydrocarbon oxyradical. In addition, two or more substituents can together form acarbocyclic or heterocyclic ring. Thus, for example, when a heterocyclicring or carbocyclic ring is the representative group, substituents on acarbocyclic ring or heterocyclic ring can together with the heterocyclicor carbocyclic ring form a ring. Thus, two or more substituents can, forexample, form an aromatic ring, an example of which would bebenzimidazolyl, which group would be included in the genericdescription, heterocyclic ring. In addition, the term heterocyclic ringis herein defined to include a heterocyclic ring which is present in acompound such as a compound represented by (A)(l) wherein R and Rtogether with a nitrogen atom to which they are attached form aheterocyclic ring in which the nitrogen atom to which R and R areattached is the sole hetero atom.

The term hydrocarbon radical is herein defined to include hydrocarbonswhich contain only carbon and hydrogen and also hydrocarbons whichcontain other elements in addition to carbon and hydrogen. The termhydrocarbon radical, Whichcontains carbon and hydrogen as well ascarbon, hydrogen and other elements, includes hydrocarbon radicals whichare completely saturated as well as hydrocarbons which haveunsaturation. Thus, the term hydrocarbon radical, in addition tohydrocarbons containing only carbon and hydrogen, includes hydrocarbonradicals containing one or more elements (such as oxygen, nitrogen andsulfur) other thna carbon and hydrogen, which elements can besubstituted upon a hydrocarbon radical or can link two or morehydrocarbon radicals. It is also contemplated that a hydrocarbon radicalcan contain both substitution and linkage by one or more elements.

Thus, substituents can be present such as aryloxy, aryl, alkyl, alkoxy,polyaryloxy, arylmercapto, acyl, aroyl, dialkylamino, monoandpolyhydroxy aryl, monoand polyacyl aryl, hydroxyand acyl-substitutedaryl, cyano, 0x0 and carboalkoxy.

Whereas all of the aforedescribed groups, that is, a hydrocarbonradical, a hydrocarbon oxy radical, a cyclic ring, a carbocyclic ringand a heterocyclic ring, are contemplated within the scope of thisinvention, such groups should be non-interfering with respect to thefunctioning of the compounds represented by (A), (B), (C) and (D). Thus,a group should be non-interfering to the extent that it does notcompletely nullify the antioxidant activity of the compounds representedby (A), (B), (C) and (D) when incorporated into a base stock. Theaforedescribed groups can be adjusted with respect to the number ofcarbon atoms present and the number of elements present in a group otherthan carbon and hydrogen such that a compound represented by (A), (B),(C) and (D) would be soluble in a particular base stock to which thesubject compound is incorporated. Thus, depending on the particular basestock, a compound represented by (A), (B), (C) and (D) can be modifiedsuch as by adjusting the chain length of the group or adjusting thebranching present in a group in order that the particular compound willbe soluble in a given base stock. As is apparent from the description ofthe aforedescribed base stocks, the solubilizing properties of the basestocks can vary and thus the solubility characteristics of the compoundsrepresented by (A), (B), (C) and (D) can be adjusted. The variousaforedescribed groups, that is, the hydrocarbon radical, the hydrocarbonoxy radical, the cyclic ring, the carbocyclic and heterocyclic rings,are non-critical features of this invention. Thus, these groups can varyover a wide range with respect to the number of carbon atoms present andthe number of elements other than carbon and hydrogen which are attachedto the various groups. Thus, in general, it is preferred that thevarious groups contain as an upper limit with respect to the number ofcarbon atoms present per equivalent weight of M, M or M of about 28carbon atoms per equivalent of M, M or M and more preferably up to about10 carbon atoms per equivalent of M, M, or M In addition, theaforedescribed groups can be defined by the number of elements otherthan carbon and hydrogen which are present per equivalent of metalrepresented by M, M or M wherein M, M, or M have their aforedescribedsignificance. Thus, for the various groups represented by a' hydrocarbonradical, a hydrocarbon oxy radical, a cyclic ring, a carbocyclic andheterocyclic ring, the upper limit of the number of elements other thancarbon and hydrogen such as oxygen, nitrogen and sulfur Which can bepresent per equivalent of M, M or M has a preferred upper limit of about6 elements per equivalent of M, M, or M and more preferably is an upperlimit of about 4 elements per equivalent of a metal represented by M, M,or M Typical examples of a hydrocarbon radical are alkyl, such asmethyl, ethyl, propyl, isopropyl, butyl, tertbutyl, amyl, hexyl, heptyl,octyl, nonyl, octadecyl; alkenyl, such as propenyl, butenyl, heptenyl,dodecenyl and the like; cycloaliphatic, such as cyclopropyl, cyclobutyl,cyclohexyl, monoand polymethyl cyclohexyl, monoand polyisopropylcyclohexyl, naphthenyl, cyclopentyl, noncyclohexenyl and the like; aryl,herein defined to include mono-, diand polynuclear hydrocarbons, such asphenyl, naphthyl and anthyryl, typical examples of aryl being phenyl,alkylphenyl, xenyl, tert-amylphenyl, naphthyl, tolyl, cresyl,halogenated phenyl, monoand polyhydroxy phenyl, dialkylamino phenyl,monoand polyacyl aryl, hydroxyand acyl-substituted aryl, cyanophenyl,alkylhydroxyphenyl, alkylchlorophenyl, algylcyanophenyl, butylcyanonaphthyl, cyclohexylphenyl, phenoxyphenyl, tertbutylphenoxyphenyl,dialkylaminophenyl and the like; aralkyl, such as benzyl, methylbenzyl,phenylethyl and the like; oxyand/or oxo-containing aliphatic,cycloaliphatic and aromatic radicals, such as aroyl, typical examples ofwhich are benzoyl, 3-methylbenzoyl, acyl such as acetyl,aryl-substituted acyl, alkoxy-substituted alkyl radicals,cycloalkoxy-substituted alkyl radical, alkenoxy-substituted alkylradical, carboalkoxy such as carboethoxy, carboalkoxy-substituted arylor alkyl radical, aroxy-substituted alkyl radical, alkoxy-substitutedcyclohexyl, aroxy-substituted cyclohexyl, carboalkoxycycloalkyl radicaland the like; and the aforedescribed groups further substituted with aheterocyclic group containing from 4 to 10 atoms optionally interruptedby from 1 to 4 hetero atoms, which can be nitrogen, sulfur or oxygen orcombinations thereof, such as substituted and unsubstituted pyridyl andthe like.

Typical examples of heterocyclic groups are fury], thienyl, piperidyl,pyrryl, thiazolyl, thiadiazolyl, pyrazinyl, pyridyl, pyrazolyl,imidazolyl, oxazolyl, pyrimidinyl or a benz derivative thereof such asbenzisoxazolyl, benzimidazolyl, benzofuranyl, benzothiazolyl,benzotriazolyl, benzoxazolyl, benzothienyl, indazolyl or isoindazolyl.

Typical examples of compounds represented by (A) (1) wherein R is and ahas a value of zero, are alkali metal salts of 2- benzoyl acetic acid,

2-(1-naphthoyl) acetic acid, 2-(2-naphthoyl) acetic acid,2,2-dimethyl-2-benzoyl acetic acid, 2,2-dimethyl-2-(l-naphthoyl) aceticacid, 2,2-dimethyl-2-(Z-naphthoyl) acetic acid,2-methyl-2-ethyl-2-benzoyl acetic acid, 2-(2-methyl-2-ethyl) aceticacid, 2,2-dimethyl-2-(2-methyl-2-ethyl) acetic acid,2,2-dimethyl-2-(3-methylbenzoyl) acetic acid,2,2-dimethyl-2-(8-hydroxyl-2-naphthoyl) acetic acid, fi-oxo-cyclohexanepropionic acid, a,a-dimethyl-fi-oxo-cyclohexane propionic acid,a-methyl-u-ethyl-fi-oxo-(3-ethylcyclohexane) propionic acid,fi-ox-3-pyridine propionic acid, a,a-dimethyl-fl-oxo-3-pyridinepropionic acid, u,u-dimethyl-B-oxo(2-methyl-3-pyridine) propionic acid,2,2-dimethyl-3-oxo-4-methyl valeric acid,2-methyl-2-ethyl-3-oxo-4-methyl valeric acid, 2,2-diethyl-3-oxo-4-methylvaleric acid, 2,2-dirnethyl-3-oxo-4-methyl hexanoic acid,2-methyl-2-ethyl-3-oxo-4-methyl hexanoic acid,2,2-diethyl-3-oxo-4-methyl hexanoic acid, 2-2-dimethyl-3-oxo-4-methyloctanoic acid, 2-methyl-2-ethyl-3-oxo-4-methyl octanoic acid and2,2-diethyl-3-oxo-4-methyl octanoic acid.

Typical examples of compounds represented by (A) (1) wherein R is and ahas a value of 1 are alkali metal salts of N,N- dimethyl malonamic acid,

N-methyl-N-butyl malonamic acid, N-methyl-N-propyl malonamic acid,N,N-dimethyl-2,2-dimethyl malonamic acid, N-methyl-N-butyl-2,2-dimethylmalonamic acid, methyl-N-propyl-2,2-dimethyl malonamic acid,N,N-dimethyl-2-methyl-2-ethyl malonamic acid,N-methyl-N-butyl-Z-methyl-2-ethyl malonamic acid,N-methyl-N-propyl-2-methyl-2-ethyl malonamic acid, N-phenyl-N-methylmalonanilic acid, N-phenyl-N-ethyl malonanilic acid, N-phenyl-N-butylmalonanilic acid, 'N-phenyl-N-methyl-Z,Z-dimethyl malonanilic acid,N-phenyl-N-ethyl-2,2-dimethyl malonanilic acid,N-phenyl-N-butyl-2,2-dimethyl malonanilic acid,N-phenyl-N-methyl-2-methyl-2-ethyl malonanilic acid,N-phenyl-N-ethyl-2-methyl-2-ethyl malonanilic acid,N-phenyl-N-butyl-2-methyl-2-ethyl malonanilic acid,2-ethoxycarbonyl-2-dimethyl acetic acid,2-ethoxycarbonyl-Z-methyl-Z-ethyl acetic acid,Z-tert-butoxycarbonyl-2,2-dimethyl acetic acid, 2-tertbutoxycarbonyl-Z-methyl-2-ethyl acetic acid, 2-(2-pyridineoxycarbonyl)-2,2-dimethyl acetic acid, 2-(4-pyridineoxycarbonyl)-2,2-dimethyl acetic acid, 2-(cyclohexaneoxycarbonyl)-2,2-dimethyl acetic acid, 2-(2-pyridineoxycarbonyl)-2-methyl-2-ethyl acetic acid, 2-(4-pyridineoxycarbonyl)-2-methyl-2-ethyl acetic acid, 2-(cyclohexaneoxycarbonyl)-2-methyl-2-ethyl acetic acid,.2-(phenoxycarbonyl)-2,2-dimethyl acetic acid,2-(phenoxyphenoxycarbonyl)-2,2-dimethyl acetic acid,2-(phenoxycarbonyl-Z-methyl)-2-ethyl acetic acid, 2-(phenoxyphenoxycarbonyl -2-methyl-2-ethyl acetic acid, 2-(ethoxysulfonyl)-2,2-dimethyl acetic acid, 2-(2-pyridineoxysulfonyl)-2,2-dimethyl acetic acid, 2-(ethoxysulfonyl)-2-methyl-2-ethyl acetic acid and 2-(2-pyridineoxysulfonyl)-2-methyl-2-ethyl acetic acid.

Typical examples of compounds represented by (A)(l) wherein R is arealkali metal salts of 1,3-indane dione, 2,4-pentane dione,

3-methyl-2,4-pentane dione,

2,4-hexane dione,

3-methyl-2,4-hexane dione, 3-acetyl-2,4-pentane dione,3-acetyl-2,4-hexane dione, 2-methyl-5,5-dimethyl-2,4-hexane dione, 1-(m-chlorophenyl) -2,4-hexane dione, 1,3-cyclohexane dione and5-tert-butyl-1,3-hexane dione,

Typical examples of compounds represented by (B) 1) are alkali metalsalts of 2-hydroxy-3-naphth0ylanilide,

o-acetyl phenol,

o-n-butyryl phenol,

2,4-diacetyl phenol,

resorcinol monoacetate,

resorcinol hexanoate,

catechol monoacetate,

catechol monohexanoate,

resorcinol monobutyrate,

catechol monobutyrate,

3,4-dimethyl catechol monoacetate, 3,4-dimethyl resorcinol monoacetate,3-methyl-4-acetyl catechol monoacetate, 3-methyl-4-acetyl resorcinolmonoacetate, 4-methyl-8-ethyl-1,3-naphthalene diol,8-butyryl-l,3-napthalene diol, l-hydroxy-S-acetoxy naphthalene,2-hydroxy-4-acetoxy acetophenone,

9 2-acetoxy-4-hydroxy acetophenone, 2,2-di-hydroxy-4,4'-diacetoxybenzophenone, 2'hydroxy-2',4,4'-triacetoxy benzophenone,Z-hydroxy-S-acetoxy-p-benzoquinone and 2-hydroxy acetophenone.

Typical examples of compounds represented by (C) (1) are alkali metalsalts of 2-cyano-2-methyl acetic acid,

2-cyano-2,2-dimethyl acetic acid, 2-cyano-2,2-diethyl acetic acid,2-cyano-2-ethyl-2-methyl acetic acid, 2-cyano-2-butyl-2-ethyl aceticacid, 2-cyano-2-hexyl-2-methyl acetic acid and 2-cyano-2,2-dihexylacetic acid.

as polyethylene glycols. Complex esters are also formed by linkingdibasic acid half esters through a glycol such as dipropylene glycol, apolyethylene glycol of 200 molecular Weight, and so forth. Permutationand combination of these methods of forming ester type lubricant fluidsare valuable as well and also it is common practice to achieve desiredproperties in the ultimate base fluid by blending different ester basestocks. Simple esters providing suitable fluids can be exemplified, forexample, by

bis(2-methylbuty1) sebacate, bis(l-methylcyclohexylmethyl) sebacate,bis(2,2,4-trimethylpentyl) sebacate, dipropylene glycol dipelargonate,

the diesters of acids such as sebacic, azelaic and adipic acid withcomplex (3 primary branched chain alcohols such as those produced by thex0 process,

polyethylene glycol 200 bis(2-ethylhexyl) sebacate,

diisoamyl adipate,

1,6-hexamethylene glycol di(Z-ethylhexanoate),

bis(dimethylamyl)azelate, di(2-ethylhexyl azelate,

di(Z-ethylhexyl) sebacate,

diisooctyl sebacate,

Z-ethylhexyl 3:5 :5 trimethylhexyl sebacate,

diisooctyl azelate,

di(3 5 :5 trimethylhexyl) sebacate,

di(1-methyl-4-ethyloctyl) sebacate,

diisodecyl azelate,

diisotridecyl azelate,

di(1-rnethyl-4-ethyloctyl) glutarate,

di(Z-ethylhexyl) adipate,

di(S-methylbutyl) azelate, di(3:5 :5 trimethylhexyl) azelate,

di(2-ethylhexy1) adipate,

di(C oxo) adipate,

bis(diethylene glycol monobutyl ether) adipate,

diisooctyl/isodecyl) adipate,

diisotridecyl adipate,

triethylene glycol di(Z-ethylhexanoate),

hexanediol 1,6-di(2-ethylhexanoate) and dipropylene glycoldipelargonate.

Ester fluids with particularly good high temperature oxidationresistance are provided by neopentyl polyol esters. The alcohols fromwhich these esters are derived have the carbon structure of neopentane,with a central carbon atom surrounded by 4 substituent carbon atoms.Included in the neopentyl polyols are neopentyl glycol,trimenthylolethane, trimethylolpropane and pentaerythritol. Generally,the base fluids comprising neopentyl polyol esters are the esters withmonocarboxylic acids. Such esters are generaly more oxidatively andthermally stable than the dibasic acid esters. The useful esters of theneopentyl polyols include, for example, the esters of trimethylolpropane, neopentyl glycol and pentaerythritol with normal, branchedchain and mixed acids having chain lengths varying from C to C Thus, anillustrative series of esters are trimethylolpropane tri-n-pelorgonate,trimethylolpropane, tricaprate, trimethylolpropane tricaprylate, thetrimethylolpropane triester of mixed octanoates, pentaerythrityltetrabutyrate, pentaerythrityl tetravalerate, pentaerythrityltetracaproate, pentaerythrityl dibutyrate dicaproate, pentaerythritylbutyrate caproate divalerate, pentaerythrityl butyrate trivalerate,pentaerythrityl butyrate tricaproate, pentaerythrityl tributyratecaproate. Suitable dipentaerythrityl esters include dipentaerythritylhexavalerate, dipentaerythrityl hexacaproate, dipentaerythritylhexaheptoate, dipentaerythrityl hexacaprylate, dipentaerythrityltributyrate tricaproate, dipentaerythrityl trivalerate trinonylate anddipentaerythrityl mixed hexaesters of C fatty acids.

Typical examples of complex esters are obtained by esterifyingdicarboxylic acids with a mixture of monohydric alcohol and a glycol togive complex esters. Complex esters which can be prepared by esterifyinga dicarboxylic acid (1 mole) with a glycol (2 moles) and amonocarboxylic acid (2 moles) or with 1 each of a glycol, a dicarboxylicacid and a monohydric alcohol or with 2 moles each of a monohydroxymonocarboxylic acid and a monohydric alcohol. Still other complex estersmay be prepared by esterifying a glycol (1 mole) with a monohydroxymonocarboxylic acid (2 moles) and a monocarboxylic acid (2 moles).

Other complex esters which are suitable are prepared by polymerizing adihydroxy compound With a dicarboxylic acid and reacting the terminalhydroxy and acid r radical with a mixture of a monocarboxylic acid and amonohydric alcohol. Specific examples of polymers which may be utilizedas additives Within the scope of this invention are polymers prepared bythe polymerization of adipic acid and 1,2-propane diol in the presenceof minor amounts of short-chain monocarboxylic acids and a monohydricalcohol to give molecular weights of the polymers thereby produced offrom about 700 to about 40,000 or higher.

The mono-, diand polyhydric alcohols, and the mono carboxylic acidsemployed in the preparation of the complex esters can also contain etheroxygen linkages.

Specific examples of suitable complex esters which are suitable basestocks are esters prepared from methylene glycol (1 mole), adipic acid(2 moles) and 2-ethylhexanol (2 moles); esters prepared fromtetraethylene glycol (1 mole), sebacic acid (2 moles), and2-ethylhexanol (2 moles); esters prepared from 2-ethyl-1:3 hexanediol (1mole), sebacic acid (2 moles) and Z-ethylhexanol (2 moles); estersprepared from diethylene glycol (1 mole), adipic acid (2 moles) andn-butanol (2 moles); esters prepared from polyglycol 200 (1 mole),sebacic acid (2 moles) and ethylene glycol mono(2-ethylbutyl) ether (2moles); esters prepared from sebacic acid (1 mole), tetraethylene glycol(2 moles) and caproic acid (2 moles); esters prepared from triethyleneglycol (1 mole), adipic acid (1 mole), n-caproic acid (1 mole) and2-ethylhexanol (1 mole); esters prepared from sebacic acid (1 mole),lactic acid (2 moles) and n butanol (2 moles); esters prepared fromtetraethylene glycol (1 mole), lactic acid (2 moles) and butyric acid (2moles); complex esters prepared from neopentyl glycol (2 moles),dicarboxylic acids (1 mole) and monocarboxylic acids (2 moles) andcomplex esters prepared from neopentyl glycol (1 mole) dicarboxylicacids (2 moles) and monohydric neoalcohols, e.g.,2,2,4-trimethylpentanol (2 moles).

In order to demonstrate the outstanding properties of the compositionsof this invention, various metal salts were blended into base stocks andthe resulting functional fluid compositions evaluated for oxidativestability and improved resistance to lead corrosion. One of the majorbench scales for evaluating the high temperature performancecharacteristics of lubricants under a selected level of severity is thehearing test.

Briefly the apparatus used in this test is an Erdco high temperaturebearing head mounted on an Erdco universal test stand. The bearing headis divided internally into two main sections. The front, or testsection, contains the test oil system and an unshielded 100 ml. straightroller bearing. The temperature of the test bearing is controlled bysupplying heat to the outer race of the bearing. The rear of supportsection of the bearing head provides for the external loading of themain shaft which transmits a radial load to the test bearing. The testand support sections of the bearing head are separated by air cell toprevent mixing of the test and support oils. The test oil temperature ismaintained by a controlled heat sump.

In conducting the test a sample of the lubricant is subjected to aselected severity (temperature) level for a 100-hour endurance period.At l-hour intervals during the test, samples of the oil are taken sothat changes in physical and chemical properties of the oil during thetest can be determined. A visual inspection is made at the end of thetest which assesses the type and extent of accumulated deposits in thetest bearing compartment. A weighted numerical rating system is used todefine the deposit condition at the end of the test. Additional data onthe relative sludge forming tendencies are obtained by monitoring theweight of air inlet screen (100 mesh) and outlet screen (40 mesh) duringthe test. Screens are changed when their pressure drop reaches p.s.i.

Oil is supplied to the bearing during the test from the sump at a rateof 600 cc. per minute through a No. 60 drill size jet located so as tosupply test oil to the bearing at approximately the 12 oclock position.Before the test proper is commenced, the bearing rig is started and thefollowing conditions are allowed to stabilize.

reported in terms of cleanliness by the use of a demerit system whichembodies the assignment of values of 0 to 20 based upon inspection ofthe bearing head and bearing. 0 designates a new or thoroughly cleancondition, whereas 20 represents the worse condition possible. Anexample of the types of deposits which can be encountered are thoseranging from what is normally termed a varnish through deposits whichare only in the form of a sludge to degrees of actual carbon coatingwhich can be a light, smooth coating to a heavy carbon deposit which isblistered or even flaky.

In addition to assigning a demerit rating to various points within thebearing head, an area demerit is also applied in determining an over-alldeposit rating. An area demerit is defined as the area covered by thedeposits divided by 10. In turn the area demerit is multiplied by thedemerit value previously assigned from the inspection to provide arating. Then in turn the rating obtained as described above ismultiplied by a weight factor to yield a demerit rating. The weightfactor takes into account the severity of the conditions which areencountered in various locations in the bearing head. For example, theweight factor for the end cover of the bearing head is one, whereas theweight factor for the bearing itself is 5. In all, 6 different locationsare inspected and rated and the foregoing system applied to arrive at ademerit for each such location. In the case of the inspection in thedetermination of demerits for the bearing, the bearing is broken downinto various categories, such as a roller case and outer and innerraces, which are individually rated to arrive at a demerit rating. Thedemerit ratings of the 6 locations which are inspected are then addedand divided by 6 to arrive at an over-all rating.

In the following examples in Table I the bearing temperature was 500 F.and the bulk oil temperature was 440 F. The base stock that was utilizedin the following examples was a mixture of short-chain pentaerythritolesters and short-chain dipentaerythritol esters having an Oil in temerature 400 F. Oil flow i 600 cc per minute average chain length ofabout 6 carbon atoms. The base Bearing speed 10 000 rpm stock wasformulated with a trlaryl phosphate and 1% Radial load 5 lbs each ofphenyl-a-naphthalene and dioctyl phenylamme. Air flow to beating headand cover 0.35 c.f.m.

TABLE I Deposit test result Concentratlon, Percent, meq/ depositviscosity Example No. Metal compound 100 g. rating increase 1 None None48 406 Potassium salt of 2,2,4-trlmethyl-3-oxo valerlc acld 0.443 24 190Potassium salt of 2-hydroxy-3-naphthoylanlhde 0.156 22 87 The 100-hourendurance test is then commenced. The 100-hour test is conducted so thatthere is at least one thermal cycle" every 17 hours of operation. Thisthermal cycle consists of a shutdown at least long enough to allow thetest oil bulk temperature to drop to 150 F., after which the temperatureis raised back to that present at the beginning of the test. Bearingstabilization and warm-up time following a shutdown is considered partof the 100-hour test time.

After completing the test and shuting down the equipment, the conditionsof the bearing and bearing head are One of the major bench scale methodsused for evaluating the lead corrosivity of various lubricantformulations is Federal Test Method Standard No. 791, Method No. 5321.1.The base stock that was used was the same base stock as was utilized forpreparing the compositions of Table I. In the above test method, 500 ml.of the test fluid is placed into a tube to which is inserted a lead testpanel. The tube is inserted in a bath which is maintained at atemperature of 375. Air is bubbled through the sample liquid atapproximately 2 cubic feet per hour. The weight loss or net weight gainof the test sample is measured after a period of 5 hours. The weightloss is measured in milligrams per square inch.

TABLE II Coneen- Weight loss lead,

tration, mg./in. Example meq./ No. Metal compound g. 1 hour 5 hours 4Potassium salt of 2,2,4-trimethyl-3-oxo valeric acid 0 22 10 Potassiumsalt of 2-hydroxy-3-naphtlroylanilide- Potassium salt of o-hydroxyacetophenone 7 Potassium salt of N-C12.14 alkyl tetrapropenylsuccinamicacid 1 Over 100.

As is demonstrated by Table I, it is clearly evident that theincorporation of the metal compounds represented by (A), (B), (C) and(D) into a base stock provides a functional fluid composition which hasa high degree of resistance towards oxidative degradation and thereforea greatly extended useful life. In regard to the extension of usefullife, it has been found that the test procedure used above correlatesquite well with the results obtained during full-scale aircraft gasturbine engine tests and under conditions of actual use. In particular,Table I clearly illustrates the reduction in deposits tendencies and thecontrol oxidation by the incorporation of a metal compound representedby (A), (B), (C) and (D). This is of particular significance since thecontrol of oxidation influences the useful life of a functional fluidcomposition. In addition, the tendencies of a functional fluid to formdeposits adversely affects the lubricating qualities and in particularthe ability of a functional fluid composition to perform its lubricantfunction. Thus, deposits can plug filters as well as critical orificesthrough which a fluid of necessity has to flow in order to lubricatecritical areas in a jet engine.

Table II significantly demonstrates the reduction in corrosiontendencies of a functional fluid composition having incorporated thereinan alkali metal compound represented by (A), (B), (C) and (D). Inparticular, Table II demonstrates the high degree of resistance towardsoxidative degradation by the incorporation of a compound represented by(A), (B), (C) and (D) while not adversely affecting other critical fluidproperties such as lead corrosion. Thus, for example, Example 7 showsthat a potassium salt of a compound not having the requisite structureof those compounds represented by (A), (B), (C) and (D) injects otherproblems and in particular adversely affects the lead corrosion. Thehigh degree of lead corrosion is well illustrated by the weight loss inlead after hours, which loss is 10 times over the compounds representedby (A), (B), (C) and (D). Thus, the oxidative stability of a functionalfluid is increased without injecting other problems such as leadcorrosion which itself can adversely affect the performance of afunctional fluid composition.

As a result of the excellent stabilization of functional fluids whichincorporate the metal compounds of this invention, lubrication of gasturbine engines is obtained over extended periods of time. Thus, thisinvention relates to a novel method of lubricating gas turbine enginewhich comprises maintaining on the bearings and other points of wear alubricating amount of a composition of this invention.

In addition, utilizing the functional fluid compositions within thescope of this invention, improved hydraulic pressure devices can beprepared in accordance with this invention which comprise in combinationa fluid chamber and an actuating fluid composition in said chamber, saidfluid comprising a mixture of one or more of the base stockshereinbefore described and a minor amount, suflicient to inhibit andcontrol corrosion damage, of the additive composition of this invention.In such a system, the parts which are so lubricated include thefrictional surfaces of the source of power, namely the pump, valves,operating pistons and cylinders, fluid motors, and in some cases, formachine tools, the Ways, tables and slides. The hydraulic system may beof either the constant-volume or the variable-volume type of system.

The pumps may be of various types, including centrifugal pumps, jetpumps, turbine vane, liquid piston gas compressors, piston-type pump,more particularly the variable-stroke piston pump, thevariable-discharge or variable displacement piston pump, radial-pistonpump, axial-piston pump, in which a pivoted cylinder block is adjustedat various angles with the piston assembly, for example, the VickersAxial-Piston Pump, or in which the mechanism which drives the pistons isset at an angle adjustable with the cylinder block; gear-type pump,which may be spur, helical or herringbone gears, variations of internalgears, or a screw pump; or vane pumps. The valves may be stop valves,reversing valves, pilot valves, throttling valves, sequence valves,relief valves, servo valves, nonreturn valves, poppet valves orunloading valves. Fluid motors are usually constantor variable-dischargepiston pumps caused to rotate by the pressure of the hydraulic fluid ofthe system with the power supplied by the pump power source. Such ahydraulic motor may be used in connection with a variable-discharge pumpto form a variable-speed transmission. It is, therefore, especiallyimportant that the frictional parts of the fluid system which arelubricated by the functional fluid be protected from damage. Thus,damage brings about seizure of frictional parts, excessive wear andpremature replacement of parts.

In addition, due to the excellent physical properties of thecompositions of this invention having incorporated therein a metalcompound represented by (A), (B), (C) and (D), heat transfer systems canbe developed wherein a liquid heat exchange medium is utilized toexchange heat with another material wherein said material is at a giventemperature. Thus, the function of the liquid heat exchange medium canbe any one or a combination of the following: transfer heat, accept heatand maintain a material at a given temperature.

The fluid compositions of this invention when utilized as a functionalfluid can also contain dyes, pour point depressants, metal deactivator,acid scavengers, antioxidants, defoamers in concentration sufiicient toimpart antifoam properties, such as from about 10 to about 100 parts permillion, viscosity index improvers such as polyalkylacrylates,polyalkylmethacrylates, polycyclic polymers, polyurethanes, polyalkyleneoxides, polyalkylene polymers, polyphenylene oxides, polyesters,lubricity agents and the like.

It is also contemplated within the scope of this invention that the basestocks as aforedescribed can be utilized singly or as a fluidcomposition containing two or more base stocks in varying proportions.The base stocks can also contain other fluids which include, in additionto the functional fluids described above, fluids derived from coal Iproducts and synthetic oils, e.g., alkylene polymers (such Theembodiments of this invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A composition comprising (A) a major amount of an ester lubricantbase stock,

and

(B) an oxidation improving amount of a material selected from the groupconsisting of compounds represented by the structure wherein Ar is anaromatic nucleus selected from the group consisting of benzene,benzoquinone and naphthalene, M is an alkali metal, R is selected fromthe group consisting of alkyl, aryl, and alkaryl hydrocarbon radicals, Ris selected from the group consisting of hydrocarbonoxy radicals,hydrocarbon radicals, and

O -O--C Ro group, b is a whole number having a value of 0 to 6, and c is0 to 1.

2. A composition of claim 1 wherein Ar is a naphthalene nucleus, R is anaromatic hydrocarbon radical, b is 0, and c is 1.

3. The composition of claim 2 wherein the oxidation improving materialis the potassium salt of 2-hydroxy-3- naphthoyl-anilide.

4. A composition of claim 1 wherein Ar is a benzene nucleus, R is analkyl radical and b and c are 0.

5. The composition of claim 4 wherein the oxidation improving materialis the potassium salt of o-hydroxyacetophenone.

6. A composition of claim 1 wherein the ester base stock is selectedfrom the group consisting of pentaerythritol esters, depentaerythritolesters, and mixtures thereof.

7. In a method of lubricating a gas turbine engine the improvement whichcomprises maintaining on the bearings and other points of wear alubricating amount of a composition of claim 1.

8. In a method of lubricating a gas turbine engine the improvement whichcomprises maintaining on the bearing and other points of wear alubricating amount of a composition of claim 3.

9. In a method of lubricating a gas turbine engine the improvement whichcomprises maintaining on the bearings and other points of wear alubricating amount of the composition of claim 5.

References Cited UNITED STATES PATENTS 2,346,156 4/ 1944 Farrington etal. 25342.7X 2,810,696 10/1957 Lowe et a1. 25242.7X 3,347,791 10/1967Thompson et al. 25242.7X

PATRICK P. GARVIN, Primary Examiner W. J. SHINE, Assistant Examiner

